Hydrogenation of catalytic naphthas



Oct'. 15, 1957 R. c. MoRBEcK ETAL 2,810,004

HYDROGENATION y.OF CATALYTIC NAPHTHAS l i Roberv C. Morbeck Roberf JLang Inventors nited States Patent() 2,810,004 HYDRGGENATION OFCATALYTIC NAIHTHAS Robert C. Morbeck, Fanwood, and Robert J. Lang,Cranford, N. J., assignors to Esso Research and Engineering Company, acorporation of Delaware Application March 1, 1955, Serial No; 491,406

2 Claims. (Cl. M50-4683.6)

This invention relates to a process for improving the quality of lightcatalytic naphthas. The invention is directed to a specifichydrogenation treatment applicable to a particular selected fraction ofa catalytically cracked naphtha. The invention. provides a means forgreatly improving the Motor method octane rating of such catalyticnaphtha fractions.

The invention involves fractionation of a catalytically cracked naphthainto at least two fractions, one of which constitutes the portion of thenaphtha boiling in the range of about 65 to 115 F. Hydrogenation of thisi lem of satisfying the octane requirements of current autofro `motiveengines. VIn, the past, octane ratings of gasolines have primarily beendetermined by the so-called Research method, which can be' determined byASTM- test, designated D908-47T. While this is an important and valuableanti-knock rating test, it has become appreciated that the Researchoctane rating of a gasoline as determined `by this method correlatespoorly with actual road perform- .ance of a gasoline. search octanenumber is determined in a test procedure This is true in part since theRe- L; rating of a gasoline is not a complete indication of the value ofa gasoline in satisfying an engine under road conditions.

As a result, other methods of determining octane ratings are commonlyemployed. One such method is the so-called Motor method test, designatedby ASTM test particular fraction provides substantial and unexpectedadvantages as regards the quality of the resultant hydrogenationproducts. The invention is based on the discovery that the fraction of acatalytic naphtha boiling in the range of about 65 to 115 F.; that is,the pentene fraction, is particularly susceptible to improvement in'ments in the Motor method octane rating. Unexpectedly,`

however, by hydrogenating the fractionof a catalytic naphtha boiling inthe range of'65" to 115"F:, it is possible to secure great improvementsyin the Motor method octane rating of this particular fraction`accompanied by little, if any, loss in the Research method octanerating. lt is 'the basic concept of this invention therefore, to providea hydrogenation treatment for upgrading the antiknock quality of thisspecific fraction of a catalytic naphtha which is separated from thenaphtha for this treatment.

In a specific embodimentof the present invention, a catalytic naphtha isdivided into the pentene fraction and a heavier naphtha fractionand bothof these fractionsl are subjected to different and specifichydrogenation conditions. By this means it is possible to upgrade thetotal' catalytic naphtha bya' hydrogenation treatment to obtain resultswhich cannot be achieved by hydrogenation of the total naphtha. t

The invention will be fully identified 'in the description whichfollows, and with reference to the accompanying drawing whichdiagrammatically illustrates aiflow plan of a specific Vand preferredembodiment of the invention. i One of the most important requirements ofa high quality gasoline at the present time relates to the antiknockrating of the gasoline; The importance of gasolines of high anti-knockrating has been made more and critical by the trend toward engines ofhigher compression ratio. At thepresent time the compression ratioMethod D357-47. It has been found that the Motor method octanedetermination correlates with the road performance of la gasolinesomewhat better than the Research octane rating. e In view of thesebasic factors, production of present day-high quality gasolines must becarried out with reference to both the Research and Motor method octaneoctane rating. The over-all octane rating of the fuel is some functionof both of these octane rating methods and can be approximated bylaverging the Research and Motor method ratings.

` It is the principal object of this invention to provide a refiningprocess particularly adapted for improving the Motor method octanerating of naphthas. This invention` therefore provides a valuable toolfor providing higher quality gasolines in a manner heretoforeunobtainable.

The nature and benefits of this invention can be apf` preciated byreference to Table I, showing data obtained by conduct of two types ofhydrogenation applied Vto selected fractions of a light catalyticnaphtha as com-` tions, approximately 98% of the oleins present in thefeed of current automobile engines has been increased to values above6.5, ranging upwardly toas high as,12. Engines having such highcompression ratios require use of high anti-knock gasolines.- The moreextended use 0f. automaiictransmssions has.. alsoiaggravatedthe probf.

were saturated. In the other hydrogenation operation employed, using thesame catalyst at the same temperature and with the same amount ofhydrogen, and at throughputs of about 1.5 to 2 v./v./hr., pressure wasmaintained at the lower figure of 50 p. s. i. g., so as to cause partialsaturation of the oleins present in theV feed. Under these'V conditions,approximately 43% of the oleins were hydrogenated to saturation. Y

In the conduct of these experiments, three types of naphtha feed stockwere employed. v The first of these constituted the whole of a lightcatalytic naphtha boiling in the range of about 65 F. to 363 F. Asecondfraction constituted only that portion of this naphtha boiling inthe range of about to 150 F. Finally, a `third hydrogenation feed stockconstituted only the pentene fraction of the light catalytic naphthaboiling.

in the range of about 65 x to 115 F. The results ofapplying thesehydrogenation treatments to these feed stocks under lthe conditionsspecified are shownv in Table i.,

TABLE I Hydrogenaton of light catalytic naphtha `oinplet sat-matanPartial saturation Oletin Saturation, -Percent 98 43 Boiling Range, FVTo 11s/15o l C15/363 C 11s/15o (1t/'aaa'D f FEP FEP Vol. Prcent on TotalNaptha 22 17 10o 22 17 `16o Octant` Change (3 cc. TEL): y

MOOI -Q. +14. O +6. 5 +4. 5 +7..0 +2.*5 +2. 5

- Net octane change +12. 5 0.5 2. 5 +8.() +1 0 +0.5

Final Motor Octane (3 coTEL) 100 9255 88.5 93 88. 5 8635 HydrogenConsumption, S. C. F./B 650 630 520 300 300 220 Referring to Table I,lit will beobserved that hydrogenation Vof the total naphtha conductedto secure complete saturationof olefins present, resulted in asubstantial drop in the Research octane rating of the gasoline. Thisyhydrogenation treatment resulted in a loss of 7 l'Research octanenumbers.A The operation caused a small improvement in the Motor octanerating of the gasoline amounting to 4:5 octane units. However, it isapparent that the substantial loss in Research octane number wouldordinarily far offset any value obtained by appreciation of the smallgain in Motor octane number. When treating the total naphtha .under themilder hydrogenation conditions, causing partial saturation ofrolenspresent, al smaller loss in VResearch octane resulted, although in thiscase the Motor octane rating of the hydrogenated naphtha improved butlittle. Again, therefore, application of this hydrogenation treatment tothe total naphtha is shown to be of little or no value so far `asimproving the overall octane quality of the gasoline.

VAs opposed vto this, the data'of Table I shows the substantial andunexpected improvement Vin the anti-knock quality obtainable whenapplying these same hydrogenation conditions only to` the pentenefraction of the naphtha. In particular, the data show that Yin thecomplete saturation hydrogenationtreatment applied to the -pentenefraction of the naphtha, itwasvpossible to increase the Motorv methodvoctane rating 'of this fraction by l14 units. Concomitantly, there waslittle change'irl the Research rating of the-pentene fraction amountingonly to a decrease of 1.5 units 'which was substantially less than thatresulting from treating the total naphtha under the same hydrogenationconditions. The partial saturation hydrogenation'treatment, when appliedto only the pentene fraction of the naphtha again showed substantialadvantages over treatment of the total naphtha. Thus, th'epartialsaturation treatmentof the pentene fraction resulted in'a gain of 7octane units vby the Motor method and of. one octane unitby the Researchmethod. The data of VTable I therefore, shows the substantial andunexpected advantages of segregating the pentene fraction lfrom acatalytic naphtha and applying a hydrogenation treatment to thisspecific fraction. ABy so doing, it becomes possible to greatly improvethe Motor octane rating of this specific fraction while avoiding thedegradatio'n inResearch octane rating otherwise resulting fromhydrogenaton of the total catalytic naphtha.

With reference to the hydrogenation ofthe intermediate naphtha'fractionboiling within the range of 115 to 150 F., the data of Tablel againshows that thislfraction can not be appreciably upgraded in octanecharacteristics. Thus, because of loss in the Research octane rating,hydrogenation of this fraction -at either p'artial'orcompletes'aturationconditions provides substantially no 'better result than treatment ofl'the total naphtha. 'This data therefore. establishes thathydrogenation vof the p'entene fraction of a catalytic naphtha byitselfprovides sig-y nificant and unexpectedA improvement 'in anti-knockcharacter'istics `not obtainable by hydrogenating the total naphthajornarrow fractions kof the naphtha other than the pentene fraction.

As Aformerly *st ated, the 'overall octane 'rating of a gasolinefisbestlitrdicated "by `a consideration of yboth the Research and Motorincthod octane rating. To weigh in :this consideration net octane change'is indicated in Table i 'which 'is simply the `sumi'of the Research andMotor method octane y'changes resulting from hydrogenation of theditfe'reiit stocks. The` unexpected and substantial advantage ofhydrogenatil'ig the pentene fraction alone'is particularly indicated 'bythe net octane change data.

The vrel'narlcable increase in the Motor Voctane rating of the pe'nteneCfraction obtainable by hydrogenation is primarily due to the increasedlead susceptibility of the hydo'genated lpentnes. -Data 4establishingthisare shown in Tablet-l. ,A l

TABLE II Motor-octane Number Feed saturated A Product Leaded (s M1.TELL-.. 86.0 99.9 +1a9 clear 81.2. l sal +o.9

A Due to 'ran +4.21 +118 These data show that while the clear octanenumber of the hydrogenated pentene fraction is but little better thanthat of the unhydrogenated fraction, remarkably, the leaded Motor octanenumber attributable to the presence of'tetraethyl-lead is increased by17.8 octane units.

An important featureqof this invention is the manner in which hydrogenis conserved while achieving improvement in anti-knock quality. VAcatalytic naphtha contains a substantial amount of olefinic constituentsresultinginhi'gh lhydrogen consumptions when such naphthas arehydrogenated For example, when hydrogenatng aitot'allight catalyticnaphtha boiling in the range of about 65 "to 363 F.,a'hydrogen'consumption of about 500 to 600 standard cubic feet perbarrel is required. From, an economic' viewpoint, this substantialconsumption of hydrogen'could not bejustied for attaining therelativelyinsignificant change in anti-knock characteristicsshown inTableAI. However, by hydrogenating onlythe-'pentene fraction of acatalytic naphtha, while about thesarne amount of hydrogen is requiredper barrel of penitene feed, over-al1 hydrogen requirements are onlyjafraction of those required for treating the total naphtha. This Ycan beappreciated by the fact that approximatelyia l2.() Motoroctan'e grainper 100 standard cubic feet *of hydrogenper barrel can be achieved bytreating `tliepentene jfraction v'while the 'Motor method octane gainintreatingthe total naphtha with the lsame`amount-ofhydrogeniSonIy'abOut0.5.. Consequently, in consideringthehydrogenation rof catalytic pentenes in accordance WiththisVinvention, opposed to hydrogenation of other fractions of a catalyticnaphtha, it is apparent that this invention provides a remarkableimprove-` ment in anti-knock quality for quantity of hydrogen required.i The data of Table I, shows thatpartial saturation of the pentenefraction attainsabout, half the improvement in Motor octane number'whichcan be obtained by total saturation. These data are particularlysignificant in considering makeup of a relinery gasoline pool. Olefinicconstituents have a more desirable octane blending factor thanparaflinicconstituents, and for this reason by partially saturating the pentenefraction as shown'in `Table I, the over-all effect in'a gasoline pool issubstantially thatl obtainable by complete saturation of the pentenefraction. Por this reason it is a particular feature of this inventionto partially saturate. rather than to completely saturate the pentenefraction of alight catalytic naphtha so as to further conserve hydrogenconsumption and to provide a pool gasoline product of substantially theoctane characteristics obtainable by. other processes requiring greateramounts of hydrogen. In this connection it is generally preferred tosaturate about 30% to 60%, for example, about 40% of the olefns presentin the pentene fraction.

While the process of this invention has a desirable effect on the sulfurcontent of naphthas treated in accordance with the invention, theprocess would not normallybe used for this purpose and cannot beconsidered a desulfurization operation. l Catalytic naphthas by theirnature are generally of low sulfur content due Yto conversion andelimination of sulfur compounds during catalytic cracking. Consequently,catalytic naphthas ordinarily have sulfur contents in the relatively lowrange of about 0.02 to 0.10%. Of this sulfur content, practically all ofthe sulfur is contained in the higher boiling fractions of the naphtha.The pentene fraction of a catalytic naphtha separated by fractionationonly contains about 0.02% of sulfur constituting less than of the totalsulfur in the naphtha. Hydrogenation of the pentene fraction even whenconducted to secure maximum desulfurization only reduces the sulfurcontent to a level of about 0.0002% to 0.001%. Thus, if thisdesulfurized pentene fraction were to be blended back with the heaviernaphtha fractions to reconstitute the total naphtha, the sulfur contentof the total naphtha would only be changed by about 5%. It is apparentthen that the process of this invention, while being of advantage insomewhat reducing sulfur content of a naphtha cannot be considered asconstituting or replacing other desulfurization operations.

In obtaining a total catalytic naphtha of highest quality, it isdesirable to particularly treat the portion of the naphtha remainingafter separation of the pentene fraction. It is particularly desirableto treat the heavier fraction of the catalytic naphtha by a hydroiningoperation conducted at hydrogenation conditions different from thoseapplied to the pentene fraction. This is achieved by hydroiining theheavier fraction of catalytic naphtha boiling above 250 F. underconditions to secure a bromine number reduction of no more than about20%. This results Vin primarily improving the engine cleanliness andstability characteristics of this naphtha fraction while contributing asulfur reduction of about one-third. Such hydrofining can be carried outusing a hydrogenation catalyst such as cobalt molybdate at temperaturesof about 400 to 700 F., at a pressure in the range of 50 to 250 poundsper square inch, throughputs of about l to 20 v./v./hr., and at hydrogenconsumptions less than 60 standard cubic feet per barrel.

In conducting the hydrogenation of the pentene fraction in accordancewith this invention, a wide variety of hydrogenation catalysts may beemployed. Preferred catalysts constitute the oxides of cobalt ormolybdenum alone or in admixture and including cobalt molybdate.Preferably, these catalytic agents are supportedY on an adsorbentsupport such as alumina. It is particularly preferred to employ cobaltmolybdat as the catalyst.` The 'pressure employed is to be in the rangeof 25 to 500 pounds per square inch although it is preferred to usepressures below 200 p. s. i. g. for the hydrogenation of the pentenefraction and it is particularly desirable to employ a pressure of about50 p. s. i. g. Throughputs of 1 to 20 v./v./hr., may be employedalthough the pre ferred range is about 5 to 10 v./v./hr. The temperaturemaintained during hydrogenation is about 500 to 800 F., and specifically700 F. Contact of the pentene frac-y tion with the catalyst under theseconditions should be carried out employing a rate of hydrogen supplyabove about 500 standard cubic feet of hydrogen per barrel, andgenerally about 1500 standard cubic feet per barrel.

The specific hydrogenation conditions are to be selected from theforegoing limits by regard to the resulting olefin saturation and/orhydrogen consumption. In general, for olefin saturations in the range ofabout 30 to 100% of the olens present in the pentene fraction, hydrogenconsumptions of about 200 to 700 standard cubic feet per barrel will beemployed. In treating a typical catalytic .pentene fraction for completeolefin saturation, a hydrogen consumption of about 650 S. C. F./B. isordinarily required.

Referring now to the drawing, a specific embodiment of thisv inventionis illustrated showing a preferred ow plan for the practice of thisinvention. l

As illustrated, a gas oil feed stock boiling in the range of about 400to 1100 F., for example, may be brought into catalytic cracking zone 1through line 2. Catalytic cracking of a conventional nature will becarried out in zone 1 permitting removal of cracked products throughline 3 for introduction to fractionation zone 4. Light gaseous productsincluding C4 and lighter hydrocarbons may be withdrawn fromfractionation zone 4 through an overhead line 5. A fraction includingthe catalytic naphtha fraction boiling in the range of about 50 to 400F., may be removed through line 6. Higher boiling cracked products willbe recovered from the fractionation zone through lower withdrawal lines7 and 8, etc.

The catalytic naphtha fraction may be passed to a secondaryfractionation system 9, which may be operated to permit removal ofresidual amounts of C4 and lighter constituents through overhead line10. In accordance with this invention, a sidestream is taken fromfractionator 9 through line 11 constituting the pentene fraction boilingin the range of about 65 to 115 F. Preferably, a higher boilingfraction, boiling in the range of about to 250 F. is withdrawn as asidestream through line 22. Finally, a fraction boiling in the range ofabout 250 to 400 F., will be removed as a bottoms product through line12.

The pentene fraction of line 11 is then passed to hydrogenation zone 14.In zone 14 the pentene fraction is subjected to hydrogenation under theconditions identied hereinbefore to achieve an olefin saturation whichis preferably about 40% or greater. The hydrogenated product may then bepassed through line 15 to zone 23 for caustic or water washing althoughthis is an optional step. Thereafter, the treated pentene fraction ispassed to storage zone 17 through line 16 for blending with othergasoline blending stocks.

In the preferred conduct of this invention, the naptha fraction of line22 is passed directly to storage zone 17. This fraction requires notreatment except optional treatment for sulfur removal. If desired,however, the naphtha of line 22 may be combined with the naphtha of line12 for treatment in hydroining zone 18. In all cases, the heavy naphthafraction of line 12 is subjected to the hydroning conditions identifiedhereinbefore. The hydrogenated product from zone 18 is then passed intothe storage zone 17 through line 20. The resultant blend of the productsof lines 16, 22, and 20 constitutes a desirable high quality gasoline.It is apparent of course that other gasoline blending stocks may also bemixed with rthese `'consftitueitfs a's desirable 'in 'conventionalrenery practice. t Y

s described, therefore, 'the present Vinvention relates to 'theupgrading of. naphth'as derived froin a catalytic cracking process. Theinvention particularly concerns the treatment of Vspeciiic, selectedfractions of a catalytic naphtha under specific hydrogenationconditions, The basic feature of the invention is ythe treatment of thepentene fraction of a catalytic naphtha boiling in the range of '65 F.Yto 115 F. 'Such afraction typically cons'titutes about 60% ofunsaturated, olenic compouds and 40% of saturated 4parains. Moreparticularly, a typical pent'ene 'fraction of catalytic naphtha willconstitute the following general composition:

The specific proportions of these 'constituents will of course varysomewhat in accordance with variationsin the conditions of catalyticcracking and the feed stock ern'- ploy'ed. Pentene 'fractions vadaptableto treatment by the present invention may, however, be characterized asconstituting at least about 50% unsaturated hydrocarbons.

What is claimed is:

. '1. A process for upgrading a catalytic naphtha which comprises thesteps of fractionating the naphtha to segregate a iirst fraction boilingbelow about 65 F.; a second fraction comprising pen'tenes free of `Cehydrocarbons and boiling 1in the` 'iaige "of about `65 F. t0 115 F.; athird ',lt'ra'ctioil boiling inthe range of about '115 F. to 250 F.`; a1fourth fraction boiling 'above vabout 250 F.; hydrogenating the secondfraction to secure an ol'eiin saturation in th range 'of 30% to V100% bycontact with hydrogen in the fpe'snce of a hydrogenation catalystselected kfro/rn the Ygroup consisting of cobalt oxide, inolyb denuinoxide and v'cobalt molybdate supported on an adsorbent carrier at a'temperature in the range of about 500 to '800 F., a pressure in therange of about 25 to 500 p. s. i., at a throughput in the range of about1 'to 20 v./v.7 hr., with 'a minimum of "500 S. C. F. of hydrogen/bbl.;`hydrgenating 'the fourth 'fraction to secure a ixirnum bromin reductionof 20% by contacting it with hydrogen inthe presence of a cobaltmolybdate catalyst at a temperature in Ythe range of 400 to 700 F., 'apressure lin 'the range of '50 to 250 lp. s. i., at a throughput in therange fof 41 to 20 v./v./hr. with amaximunrhydrogen consumption of lessthan about S, C. F-.7bbl. and* blending the third fraction with thetreated second Vand fourth'ractions to'provide a naphtha product.

2. The process of claim l in which an oleiin saturation of 'abouty30% to"60% is obtained.

A' References "Cited in 'the tile of this patent UNiTED .STATES PATENTSl2,348,557 SMattox May 9, 1944 2,860,253 Marschner Oct. 10, 1944l2,'420g030 Brandon May 6, 1947 2,426,903 'Sweeney -...2-a sept. 2, 1947

1. A PROCESS FOR UPGRADING A CATALYTIC NAPHTHA WHICH COMPRISES THESTERPS OF FRACTIONATING THE NAPHTHA TO SEGREGATE A FIRST FRACTIONBOILING BELOW ABOUT 65*F.; A SECOND FRACTION COMPRISING PENTENES FREE OFC6 HYDROCARBONS AND BOILING IN THE RANGE OF ABOUT 65*F. TO 115*F.; ATHIRD FRACTION BOILING IN THE RANGE OF ABOUT 115*F. TO 250*F., A FOURTHFRACTION BOILING ABOVE ABOUT 250*F.; HYDROGENATING THE SECOND FRACTIONTO SECURE AN OLEFIN SATURATION IN THE RANGE OF 30% TO 100% BY CONTACTWITH HYDROGEN IN THE PRESENCE OF A HYDROGENATION CATALYST SELECTED FROMTHE GROUP CONSISTING OF COBALT OXIDE, MOLYBDENUM OXIDE AND COBALTMOLYBDATE SUPPORTED ON AN ADSORBENT CARRIER AT A TEMPERATURE IN THERANGE OF ABOUT 500* TO 800*F., A PRESSURE IN THE RANGE OF ABOUT 25 TO500 P.S.I., AT A THROUGHPUT IN THE RANGE OF ABOUT 1 TO 20 V./V./HR.,WITH A MINIMUM OF 500 S, C. F. OF HYDROGEN/BBL.; HYDROGENATING THEFOURTH FRACTION TO SECURE A